Green synthesis of silver and gadolinium doped nanoparticles from Ceratonia siliqua leaves extract: Characterization, antibacterial effect and molecular docking

In the current study, silver nanoparticles (AgNPs) and Gadolinium-doped silver nanoparticles (Gd@AgNPs) were synthesized using Ceratonia siliqua leaf extract, as the reducing medium. NPs were characterized by X-ray Powder Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscope (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray technique (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-vis spectroscopy (UV-vis), Photoluminescence (PL), and Vibrating Sample Magnetometer (VSM). To evaluate the antibacterial activity of the NPs, broth microdilution, antibiofilm screening, and time-kill assay were performed. The XRD patterns revealed the synthesis of face-centered cubic (fcc) structure of metallic silver. The average crystallite sizes calculated using the Debye-Scherrer equation were found to be 20.38 nm for AgNPs and 17 nm for Gd@AgNPs, demonstrating the successful incorporation of Gd into the silver lattice without the formation of secondary phases at a doping concentration of less than 7%. The findings demonstrated that the synthesized NPs displayed a remarkable antibacterial activity against gram-positive bacteria, and gram-negative bacteria. Moreover, docking analysis demonstrated that AgNPs and Gd@AgNPs exert inhibitory effects on critical bacterial enzymes, including DNA gyrase, penicillin-binding proteins (PBPs), KPC-2 carbapenemase, and dihydropteroate synthase (DHPS). These findings provide insight into the molecular mechanisms driving the antibacterial efficacy of AgNPs, associating enzyme inhibition with reduced microbial virulence. Notably, the study underscores the superior performance of Gd@AgNPs, highlighting their potential as versatile agents with antibacterial properties. Furthermore, both NPs demonstrated inhibitory effects on both bacterial biofilms’ formation and pre-formed biofilms. These results demonstrated that both NPs could be developed as an antibacterial in combating pathogenic microorganisms.